1 files changed, 52 insertions, 8 deletions
diff --git a/src/Board/Board.ts b/src/Board/Board.ts
index ef4b4a5..b114ff1 100644
--- a/src/Board/Board.ts
+++ b/src/Board/Board.ts
@@ -57,7 +57,58 @@ export default class Board {
   }
 
   getAttachments(tile: Tile): Attachment[] {
-    return _.flatten(this.tiles.map(attachTo => attachTo.getAttachments(tile)));
+    return _
+      .flatten(this.tiles.map(attachTo => attachTo.getAttachments(tile)))
+      .filter((attachment: Attachment) => this.isLegalAttachment(attachment));
+  }
+
+  previewAttachment(attachment: Attachment) {
+    console.log(attachment);
+    const previewBoard = _.cloneDeep(this);
+    previewBoard.attach(attachment);
+    previewBoard.print();
+  }
+
+  isLegalAttachment(attachment: Attachment) {
+    const { tile, side, attachTo, orientation } = attachment;
+
+    const xIncrement = {
+      [East]: 1,
+      [West]: -1,
+    };
+
+    const yIncrement = {
+      [North]: 1,
+      [South]: -1,
+    };
+
+    const position = {
+      x: attachTo.position.x + (xIncrement[side] || 0),
+      y: attachTo.position.y + (yIncrement[side] || 0),
+    };
+
+    const isBusy = _.find(this.tiles, { position });
+    if (isBusy) return false;
+
+    // TODO: compute this array at runtime
+    const neighborIncrements = [
+      { x: 0, y: -1, side: 0 },
+      { x: -1, y: 0, side: 1 },
+      { x: 0, y: 1, side: 2 },
+      { x: 1, y: 0, side: 3 },
+    ];
+
+    return _.every(_.map(neighborIncrements, ({ x, y, side }) => {
+      const neighbor = _.find(this.tiles, {
+        position: {
+          x: position.x + x,
+          y: position.y + y,
+        }
+      });
+      if (!neighbor) return true;
+      if (neighbor.getSide(side) !== tile.getSide(side - orientation + 2)) return false;
+      return true;
+    }));
   }
 
   attach(attachment: Attachment) {
@@ -86,11 +137,4 @@ export default class Board {
 
     this.tiles.push(tileOnBoard);
   }
-
-  previewAttachment(attachment: Attachment) {
-    console.log(attachment);
-    const previewBoard = _.cloneDeep(this);
-    previewBoard.attach(attachment);
-    previewBoard.print();
-  }
 }